The present invention relates in general to feeders for transporting sheets from a sheet stack, and more particularly, to a scuff feeder for reliabily transporting sheets from the bottom of a stack of sheets without marking of the sheets.
In modern reproduction apparatus, such as electrostatographic copiers or printers, for example, a latent image of information to be reproduced is formed on a uniformly charged dielectric member to altering the charge in an image-wise pattern. The latent image charge pattern is then developed with pigmented marking particles. Thereafter, the developed image is transferred to a receiver member and fixed to the receiver member by application of heat and/or pressure to form the desired reproduction.
In order to improve productivity of reproduction apparatus, certain reproduction apparatus provide sheet feed paths capable of enabling the apparatus to reproduce information on both sides of receiver sheets. This is commonly referred to as duplex copying. Duplex copying may be accomplished in a single pass through the reproduction cycle of a reproduction apparatus (single pass duplexing), or in two passes through the reproduction cycle (double pass duplexing). For single pass duplexing, developed images of appropriate information are transferred respectively to each side of a receiver sheet and then fixed simultaneously to the receiver sheet. On the other than, for double pass duplexing, a sheet feed path is provided having an intermediate tray in which sheets, after having developed images transferred and fixed respectively on one side thereof, are stored and then at a subsequent time fed seriatim from the intermediate tray to have developed images transferred and fixed respectively on the opposite side thereof.
While double pass duplex copying is typically somewhat slower in overall reproduction productivity than single pass duplex copying, double pass duplex copying does simplify handling of receiver sheets during transport to the fixing device. This is due to the fact that only one side of the respective receiver sheets bears an unfixed toner image. However, the use of an intermediate tray in reproduction apparatus for enabling the production of duplex copies does expose the reproduction apparatus to the possibility of encountering several operational problems. Specifically, after the first side reproduction is formed on a sheet, the toned image on the first side may be soft due to insufficient time for the marking particles comprising the toned image to completely cool for fixing of the image to the sheet. This may result in fresh toner rubbing off one sheet onto the next sheet, as the sheets are fed from the intermediate tray, forming undesirable marks on such next sheet. Additionally, it is common practice to use an offset preventing oil (for example, a silicone oil) in the reproduction apparatus fusing mechanism. Some quantity of this offset preventing oil from the fusing mechanism may be deposited on the surfaces of the sheets when the fusing mechanism is used to fix the first side reproductions to the sheets respectively. As a result, the oil may materially alter the coefficient of friction in the mechanism for feeding sheets from the intermediate tray, thereby interfering with reliable feeding of the sheets from the intermediate tray (may result in misfeeds or multifeeds).